Vacuum infusion or VARTM is a process used for moulding fibre composite mouldings, where uniformly distributed fibres are layered in a first mould part, the fibres being rovings, i.e. bundles of fibre bands, bands of rovings or mats, which are either felt mats made of individual fibres or woven mats made of fibre rovings. A second mould part, which is often made of a resilient vacuum bag, is subsequently placed on top of the fibre material. By generating a vacuum, typically 80 to 95% of the total vacuum, in the mould cavity between the inner side of the first mould part and the vacuum bag, the liquid polymer or resin can be drawn in and fill the mould cavity with the fibre material contained herein. So-called distribution layers or distribution tubes, also called inlet channels, are used between the vacuum bag and the fibre material in order to obtain as sound and efficient a distribution of polymer as possible. In most cases the polymer applied is polyester, vinyl ester or epoxy, and the fibre reinforcement is most often based on glass fibres or carbon fibres, but may also be plastic fibres, plant fibres or metal fibres.
During the process of filling the mould, a vacuum, said vacuum in this connection being understood as an under-pressure or negative pressure, is generated via vacuum outlets in the mould cavity, whereby liquid polymer is drawn into the mould cavity via the inlet channels in order to fill said mould cavity. From the inlet channels the polymer disperses in all directions in the mould cavity due to the negative pressure as a flow front moves towards the vacuum channels. Thus, it is important to position the inlet channels and vacuum channels optimally in order to obtain a complete filling of the mould cavity.
In order to obtain an efficient evacuation of the mould cavity, the vacuum channels are connected to a vacuum source, such as a compressor or a vacuum pump. The vacuum channels are often connected to the vacuum source via a resin vessel or overflow bucket, so that resin, which is inadvertently sucked into the vacuum channels is spilled into the resin vessel without damaging the vacuum source. Typically a number of resin vessels are used for the evacuation process and/or the impregnation process, the number of resin vessels depending on the size of the composite structure to be manufactured.
The resin vessels may be provided with different valves and electronic equipment, such as a pressure sensor to monitor the vacuum level of the mould cavity and a resin level transmitter for measuring the amount of resin spilled into the resin vessel. Thus, the evacuation process and/or the impregnation process can be monitored closely. The valves and electronic equipment are usually disposed on top of the resin vessel, e.g. on a removable lid.
However, it has been found that a green fluid is generated, when water is mixed with the polyester resin and the resin starts hardening in the resin vessel. In the process, the water boils up and a gaseous fluid is generated, which disposes itself as a green liquid, clogging up the valves and electronic equipment disposed on top of the resin vessel. The green liquid comprises styrene and water. Consequently, the valves and electronic equipment, which are often quite expensive, will in time have to be exchanged due to the styrene and water clogging up the equipment.
U.S. Pat. No. 5,141,533 (D1) describes a method of filtering, at the end user's home, business or the like, a gas stream in which benzo-a-pyrene has been concentrated at sufficient levels to be a significant health hazard. The filter comprises a first layer with pleated filter paper, a second layer comprising a silica gel, and a third layer with active coal. Additionally, a fourth layer is arranged between the second and the third layers.
U.S. Pat. No. 5,922,105 (D2) describes a class 10,000 clean room. Air entering the cleanroom is first passed through a pre-filter and an air conditioner after which the air is deprived of dust particles via a HEPA-filter. Air within the clean room is first dehumidified via an electronic dehumidifier. The dehumidified air is then run through a HC adsorbent apparatus which may comprise a layer of silica gel and a layer of active charcoal.
GB2432336 (D3) a mould system for use in a light Resin Transfer Moulding (RTM) process. The mould system comprises a catch-pot for capturing excess resin.
US2004/157519 (D4) describes a RTM mould system. In one embodiment, a vacuum pump is used for initially collapsing a bag via a vacuum line. During a subsequent pressurised infusion process, the vacuum line is used as a drain line for draining excess resin to a pot.